By: Jeanne Anderson
The use of soft-metricated reinforcing steel as the metric standard for rebar in the U.S. has been officially adopted. Specifications for soft-metric
rebar are now available from American Society for Testing and
Materials (ASTM) and the American Association of State Highway &
Transportation Officials (AASHTO). After polling rebar producer
members, Victor Walther Jr., Concrete Reinforcing Steel
Institute (CRSI) president, said the new soft metricated rebar
was made available by various producers beginning in December,
and that the majority of the producers will have such products
available sometime during the first quarter of 1997.
"AASHTO has recommended and approved the use of soft-metric in
all highway construction," Walther told ROADS & BRIDGES. "ASTM
[also] has developed the soft-metric specifications as the
current rebar spec." With the use of soft-metricated rebar, the
inch-pound bar sizes will eventually become nonexistent.
The initial conversion method for reinforcing steel was hard
metrication, which reduced the existing 11 inch-pound bar sizes
to eight new hard-metricated rebar sizes. "Everyone thought that
it would be a nice opportunity to change the old existing
system, inch-pounds, to a hard metric system, which eliminated
three of the bars," Walther said.
The move towards
metrication of reinforcing steel began with the 1975 Metric
Conversion Act and was further accelerated by the 1988 Omnibus
Trade and Competitiveness Act.
The metrication program
was to be accomplished on a "voluntary" basis, but according to
Walther, no one in the private or public sector used them
because they would have to change their designs to accommodate
the eight new bar sizes.
In 1988, the Omnibus Trade and
Competitiveness Act was passed, stating that in order to get
federal funding for federal projects, metric products must be
used. Because using the hard-metric rebar sizes was not required
in the private-sector construction market, which represented 70%
of the total construction market, this market stayed with the
inch-pound bar sizes. With 30% of the federally funded market
using the newly specified eight bar sizes, and the remaining 70%
of the market staying with the 11 inch-bar sizes, a new problem
was created--19 bar sizes.
The reinforcing steel industry
conducted an in-depth analysis of the economic impact on the
construction industry of having to carry two complete inventory
systems. The analysis determined that this dual inventory system
would cost the end consumer $300 million per year.
Their
solution to the problem, according to Walther, was to implement
soft-metricated reinforcing steel. By using this approach to
metrication, the existing 11 inch-pound sizes physically remain
unchanged.
The only necessary change would then be to
develop new soft-metric names for those existing rebars, giving
the metric equivalent to the old bar sizes. The inch-pound size
is the name of the bar expressed in eighths of an inch in
diameter. A #6 bar is 6-in. diam. In the metric system, the bars
are renamed, using millimeters. A #10 metric bar is 10-mm diam.
Thus, a #6 inch-pound bar size is now a #10 soft-metricated bar
size.
"In essence, we're staying with the 11 bar sizes
that we always had, which are still being produced, but they
have a new name," Walther said." We've eliminated the need for
the eight new hard-metric sizes, they don't exist anymore, so
there's not the increase of $300 million per year to the
industry, and ultimately, to the consumer."
By federal
law using soft-metricated rebar is already required. For
federal-funded highway construction it started in September 1996
and for the General Service Administration federally funded
construction started in January 1994. November 28, 1995
President Clinton signed a bill that extended the requirement
date to the year 2000.
"We started in 1975, everyone
embraced it, all in good faith--it was a noble experiment that
the specs were changed to accommodate new hard-metric sizes, but
no one wanted to use them because it would cost them money to
change all of their design standards and all of the things that
they were used to all of these years."
